Waste from businesses and industries is generally stored in large, wheeled metal bins referred to as "dumpsters" which are designed to be emptied mechanically by specially equipped garbage trucks having hydraulically-operated lifting arms or forks which engage, lift and tip the dumpster. It is important that water be kept out of such containers, since users pay for removal by weight. To avoid becoming filled with rainwater, a lid must be provided for the dumpster which is hinged to permit filling and emptying of the dumpster. Such lids are metal and are generally formed in two parts due to the large weight of such lids. Even so, such lids are difficult for a user to lift and also leak some water into the container. The lids also tend to become bent when dumping into a full garbage truck, as the lid presses against the mound of trash. Such bending adds to the leakage problem in the container.
It is also useful to be able to lock the dumpster lid, to avoid unauthorized persons placing waste in the dumpster. It is preferable that the driver of the garbage truck need not have a key for the lock, nor have to descend from the truck in order to unlock the lid.
Various systems have been proposed for rendering dumpster lids easier to open. For example Hodge U.S. Pat. Nos. 3,989,162; 4,014,457; 4,098,429; 4,148,411 and Re. 30,890 disclose a lid system in which rollers or sliders assist the initial partial opening of the lid, while a pivot arm allows the lid to hang freely when dumping. In other variants of the Hodge design, stops on the inner surface of the lid hold the lid in a partially opened position. Such designs require counter-weights on the lid, and rollers tend to malfunction under the rigorous conditions under which dumpsters are used. U.S. Pat. No. 4,609,117 also discloses a lid assembly in which a curved lid is assisted in partially opening by counterweight springs, and which swings freely when inverted